1. Field of the Invention
The present invention relates generally to retractable coverings for architectural openings and more particularly to a spool about which a lift cord can be wrapped and unwrapped while extending and retracting the covering.
2. Description of the Relevant Art
Retractable coverings for architectural openings can assume numerous forms including retractable shades, venetian blinds, vertical blinds, cellular shades, and the like. In such coverings, a lift cord is typically utilized to move the covering between extended and retracted positions and the lift cord is sometimes wrapped around a spool, rod, or the like during a retracting movement. Lift cords can become entangled on the spool thereby inhibiting error-free operation of the covering and, accordingly, systems have been devised for discouraging entanglement of a lift cord.
One system for preventing entanglement is to provide a thread on the lift cord spool so that the cord is confined within the thread as it is wrapped about the spool and is therefore discouraged from becoming entangled. Another system for preventing entanglement consists of providing a surrounding housing to the spool which is closely spaced from the outer winding surface of the spool whereby only a single layer of cord is allowed on the spool thereby discouraging entanglement.
One cause of entanglement, when using a thread to confine the lift cord, resides in the lift cord being frictionally trapped within the thread and not being readily separated from the thread as the cord is being unwrapped from the spool and accordingly a system for assuring the removal of a lift cord from the thread of a lift spool during an extending movement of the covering would be desirable.